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Biomedical subjects

N Kodama

Publications and source records attributed to N Kodama.

At least 19 recordsLinked to original sources
PubMed2002

A new neuromodulatory pathway with a glial contribution mediated via A(2a) adenosine receptors.

A low concentration (10 nM) of adenosine potentiated hippocampal neuronal activity via A(2a) adenosine receptors without affecting presynaptic glutamate release or postsynaptic glutamatergic conductance. Adenosine inhibited glutamate uptake through the glial glutamate transporter, GLT-1, via A(2a) adenosine receptors. In addition, adenosine stimulated GLT-1-independent glutamate release from astrocytes, possibly in response to a rise in intracellular Ca(2+), via A(2a) adenosine receptors involving PKA activation. Those adenosine actions could lead to an increase in synaptic glutamate concentrations responsible for the potentiation of hippocampal neuronal activity. The results of the present study thus represent a novel neuromodulatory pathway with a glial contribution, bearing both inhibition of GLT-1 function and stimulation of glial glutamate release, as mediated via A(2a) adenosine receptors.

Adenosine↗
PubMed2001

Role of glial glutamate transporters in the facilitatory action of FK960 on hippocampal neurotransmission.

We found previously that N-(4-acetyl-1-piperazinyl)-p-fluorobenzamide monohydrate (FK960) facilitated hippocampal neurotransmission in the dentate gyrus of rat hippocampal slices. The present study was conducted to understand the mechanism underlying the facilitatory action of FK960. The facilitation was inhibited by H-89, an inhibitor of cAMP-dependent protein kinase (PKA), but it was not affected by cycloheximide, a protein synthesis blocker. In cultured rat hippocampal neurons, the drug had no effect on either spontaneous miniature excitatory postsynaptic currents or whole-cell membrane currents evoked by glutamate, kainate, or NMDA, suggesting that the facilitatory action of FK960 is not caused by increasing presynaptic transmitter release or excitatory postsynaptic conductances. FK960 inhibited responses of the glial glutamate transporter, GLT-1, expressed in Xenopus oocytes, and a similar effect was found with cultured rat astrocytes. The FK960 action was inhibited in the presence of H-89. The results of the present study thus suggest that FK960 facilitates hippocampal neurotransmission by inhibiting GLT-1 glial glutamate reuptake via a PKA pathway, thereby increasing synaptic glutamate concentrations.

Amino Acid Transport System X-AG↗
PubMed2001

Effects of maitake (Grifola frondosa) D-Fraction on the carcinoma angiogenesis.

We have reported that D-Fraction extracted from maitake (Grifola frondosa), activates immune competent cells, and indicates anti-tumor activities. The D-Fraction was observed to induce angiogenesis in vivo and to enhance the proliferation capability and migration capability of human vascular endothelial cell in vitro. The D-Fraction also increased plasma vascular endothelial growth factor (VEGF) concentration significantly. Also VEGF and TNF-alpha production by the activated peritoneal macrophages were enhanced. These results suggest that the anti-tumor activity of the D-Fraction is not only associated with the activation of the immuno-competent cells but also possibly related to the carcinoma angiogenesis induction.

Animals↗
PubMed2001

Monoclinic superstructure of SrMgF4 with perovskite-type slabs.

Crystals of Ce-doped SrMgF4, strontium magnesium tetrafluoride, have been found to have a monoclinic P2(1) structure with doubled a and tripled c cell lengths compared with the orthorhombic Cmcm structure previously reported in the literature. The perovskite-type slabs, composed of corner-sharing MgF6 octahedra and Sr atoms, are stacked along the b axis. The six crystallographically independent MgF6 octahedra are rotated so as to provide long periodicities along a and c. The coordination numbers and bond distances around the six crystallographically independent Sr atoms are slightly different in each case. In the superstructure, the Sr atoms lie on local mirror planes which are thought to originate at the high-temperature phase transition.

Journal Article↗
PubMed2001

Cloning of a cDNA for a constitutive NRT1 transporter from soybean and comparison of gene expression of soybean NRT1 transporters.

We have isolated a cDNA for a putative transporter, named GmNRT1-3, in the NRT1 family from soybean. It was predicted to have a similar topological structure not only to both GmNRT1-1 and GmNRT1-2 reported previously, but also to other members of the family. Two other cDNAs isolated have parts of the sequence for putative NRT1 transporters, GmNRT1-4 and GmNRT1-5, suggesting that at least five NRT1 transporters occur in soybean. These GmNRT1 genes and the GmNRT2 gene, encoding a soybean NRT2 nitrate transporter, showed different expression patterns to each other under various nitrogen conditions. Specifically, GmNRT1-3 was constitutively expressed in both roots and leaves, while GmNRT1-2 was gradually expressed as the roots developed in the presence of ammonium as a nitrogen source, but not in the presence of both ammonium and nitrate. Based on these results, we discussed the possible regulation in the expression and role of these transporters in nitrate uptake.

Anion Transport Proteins↗
PubMed2001

Catalase catalyzes nitrotyrosine formation from sodium azide and hydrogen peroxide.

Sodium azide (NaN3) is known as an inhibitor of catalase, and a nitric oxide (NO) donor in the presence of catalase and H2O2. We showed here that catalase-catalyzed oxidation of NaN3 can generate reactive nitrogen species which contribute to tyrosine nitration in the presence of H2O2. The formation of free-tyrosine nitration and protein-bound tyrosine nitration by the NaN3/catalase/H2O2 system showed a maximum level at pH 6.0. Free-tyrosine nitration induced by peroxynitrite was inhibited by ethanol and dimethylsulfoxide (DMSO), and augmented by superoxide dismutase (SOD). However, free-tyrosine nitration induced by the NaN3/catalase/H2O2 system was not affected by ethanol, DMSO and SOD. NO2- and NO donating agents did not affect free-tyrosine nitration by the NaN3/catalase/H2O2 system. The reaction of NaN3 with hydroxyl radical generating system showed free-tyrosine nitration, but no formation of nitrite and nitrate. The generation of nitrite (NO2-) and nitrate (NO3-) by the NaN3/catalase/H2O2 system was maximal at pH 5.0. These results suggested that the oxidation of NaN3 by the catalase/H2O2 system generates unknown peroxynitrite-like reactive nitrogen intermediates, which contribute to tyrosine nitration.

Animals↗
PubMed2001

Technique for fixing a temporalis muscle using a titanium plate to the implanted hydroxyapatite ceramics for bone defects.

We devised a technique to fix the temporalis muscle to the transplanted hydroxyapatite implant by using a titanium plate, which is fixed to the hydroxyapatite ceramic implant by screws and achieves good clinical results. The size, shape, and curvature of the hydroxyapatite ceramic implants were determined according to full-scale models fabricated using the laser lithographic modeling method from computed tomography data. A titanium plate was then fixed with screws on the implant before implantation, and then the temporalis muscle was refixed to the holes at both ends of the plate. The application of this technique reduced the hospitalization time and achieved good results esthetically.

Adolescent↗
PubMed2001

Addition of Maitake D-fraction reduces the effective dosage of vancomycin for the treatment of Listeria-infected mice.

Maitake D-fraction, beta1,6-glucan having beta1,3-branches, has been reported to activate the immune system of the host. To elucidate whether the D-fraction can reduce the clinical effective dosage of antibiotics in the treatment of opportunistic bacterial infection, we examined the effects of D-fraction on the treatment of Listeria monocytogenes-infected mice in combination with vancomycine (VCM), the only antibiotic used for methicillin-resistant Staphylococcus aureus (MRSA). Listeria-infection was introduced by its inoculation into the abdominal cavity of mice. Without treatment, all inoculated mice died within 3 days after the inoculation. In contrast, in the mice treated with combined therapy of D-faction (10 mg/kg per day) and VCM (10 mg/kg per day), the survival rate was maintained at 60% on the 10th day after the inoculation, which was superior to that of mice treated with VCM alone (10 mg/kg per day). To investigate the mechanism underlying the reinforcement of VCM treatment by the D-fraction, the activities of macrophages and splenic T cells of Listeria-infected mice were evaluated. In mice administered with both D-fraction and VCM, macrophages produced 2.7 times as much interleukin-1 as that of non-treated control mice. The bactericidal activity of splenic T cells was also enhanced by 2.6 times of that of non-treated control mice. These results indicate that D-fraction activates immuno-competent cells, induced cytokine production, and consequently enhanced the bactericidal activities of the splenic T cells against Listeria monocytogenes, suggesting the clinical benefit of D-fraction in the case of anti-bacterial treatment for patients with high risks.

Abdomen↗
PubMed2001

Three-dimensional computerized tomography angiography-guided surgery of acutely ruptured cerebral aneurysms.

OBJECT: The aim of this study was to assess whether aneurysm surgery can be performed in patients with ruptured cerebral aneurysms by using three-dimensional computerized tomography (3D-CT) angiography alone, without conventional catheter angiography. METHODS: In a previous study, 60 patients with subarachnoid hemorrhage (SAH) from ruptured aneurysms were prospectively evaluated using both 3D-CT and conventional angiography, which resulted in a 100% accuracy for 3D-CT angiography in the diagnosis of ruptured aneurysms, and a 96% accuracy in the identification of associated unruptured aneurysms. The results led the authors to consider replacing conventional angiography with 3D-CT angiography for use in diagnosing ruptured aneurysms, and to perform surgery aided by 3D-CT angiography alone without conventional angiography. Based on the results, 100 consecutive patients with SAH who had undergone surgery in the acute stage based on 3D-CT angiography findings have been studied since December 1996. One hundred ruptured aneurysms, including 41 associated unruptured lesions, were detected using 3D-CT angiography. In seven of 100 ruptured aneurysms, which included four dissecting vertebral artery aneurysms, two basilar artery (BA) tip aneurysms, and one BA-superior cerebellar artery aneurysm, 3D-CT angiography was followed by conventional angiography to acquire diagnostic confirmation or information about the vein of Labbé, which was needed to guide the surgical approach for BA tip aneurysms. All of the ruptured aneurysms were confirmed at surgery and treated successfully. Ninety-three patients who underwent operation with the aid of 3D-CT angiography only had no complications related to the lack of information gathered by conventional angiography. The 3D-CT angiography studies provided the authors with the aneurysm location as well as surgically important information on the configuration of its sac and neck, the presence of calcification in the aneurysm wall, and its relationship to the adjacent vessels and bone structures. CONCLUSIONS: The authors believe that 3D-CT angiography can replace conventional angiography in the diagnosis of ruptured aneurysms and that surgery can be performed in almost all acutely ruptured aneurysms by using only 3D-CT angiography without conventional angiography.

Adult↗
PubMed2001

Spinal evoked potentials following transcranial magnetic stimulation.

Motor evoked potentials by magnetic stimulation is less invasive and causes no pain as opposed to high current electric stimulation. However, the distribution of the magnetic field generated by the round coil has not been fully studied. In this report, we mapped the extent of the magnetic induction flux density, and then the evoked potentials from the spinal cord were investigated by transcranial magnetic stimulation. We also examined the origin of the evoked potentials obtained by the magnetic stimulation. The following results were obtained. The magnetic induction flux density was at its maximum at the edge of the coil. The potentials consisted of a first negative wave and subsequent multiphasic waves. The first negative wave was similar to a response of the subcorticospinal tract in the lower brain stem, while the subsequent multiphasic waves were similar to those of the pyramidal tract. Although magnetic stimulation has certain advantages over electric stimulation, several problems remain to be solved for the monitoring of motor functions in the clinical settings.

Animals↗
PubMed2001

Antidromic effect of calcitonin gene-related peptide containing nerves on cerebral arteries in rats--a possible role of sensory nerves on cerebral circulatio.

It has generally been thought that the neurogenic control of cerebral circulation is decided mainly by the autonomic nervous system. Recent studies, however, indicate that sensory nerves rich in calcitonin gene-related peptide (CGRP) are also distributed on cerebral arteries. CGRP is one of neuropeptides that has strong vasodilative effect. This indicates that sensory nerves may antidromically dilate cerebral arteries mediated by CGRP. The aim of this study is to investigate the relationship between the CGRP containing nerves and cerebral circulation. Firstly, we developed a selective denervation model of CGRP containing nerves. The denervation was performed with intrathecal administration of capsaicin in rats. Secondly, we measured the change of regional cerebral blood flow (rCBF) during the occlusion of bilateral common carotid artery or systemic hypotension. CGRP immunoreactivity around cerebral arteries disappeared after capsaicin treatment. The rCBF during the occlusion of bilateral common carotid artery decreased more in the capsaicin group than in the control group. There was no significant difference in the changes of rCBF during systemic hypotension. These results showed that CGRP containing nerves would participate in the vascular response of cerebral arteries. It is likely that sensory nerves with CGRP should have antidromic effect on cerebral circulation.

Animals↗
PubMed2000

Cisternal irrigation therapy with urokinase and ascorbic acid for prevention of vasospasm after aneurysmal subarachnoid hemorrhage. Outcome in 217 patients.

BACKGROUND: Cisternal irrigation therapy with urokinase and ascorbic acid was introduced to prevent symptomatic vasospasm after aneurysmal subarachnoid hemorrhage (SAH). To dissolve and wash out the subarachnoid clot, cisternal irrigation with urokinase is used. Ascorbic acid is added to degenerate oxy-hemoglobin, one of the strongest spasmogenic substances, into verdohemelike products, which are nonspasmogenic. The efficacy and safety of this therapy were evaluated. METHODS: This therapy was performed consecutively in 217 patients. The degree of SAH of the patients was classified as Fisher CT Group 3, and the highest CT number (Hounsfield number) exceeded 60 in the SAH, which suggested a significant risk for symptomatic vasospasm. All patients underwent surgery within 72 hours from the onset of SAH. After clipping the aneurysm, irrigation tubes were placed in the Sylvian fissure (inlet) unilaterally or bilaterally and in the prepontine or chiasmal cistern (outlet). Lactated Ringer's solution with urokinase (120 IU/mL) and ascorbic acid (4 mg/mL) was infused at a rate of 30 mL/hour/side for approximately 10 days. RESULTS: Of the 217 patients studied, symptomatic vasospasm was observed in 6 cases (2.8%), and two of these six cases (0.9%) demonstrated sequelae. The average total blood volume calculated from the drainage fluid was approximately 114 mL. Analysis of the absorption spectrum of the drainage fluid revealed disappearance of the oxy-hemoglobin-specific 576-nm peak. Complications occurred in eight patients during irrigation therapy; two patients experienced seizures, two patients developed meningitis, and four patients had an intracranial hemorrhage. However, all of these patients recovered without neurological deficits. CONCLUSIONS: These results suggest that cisternal irrigation therapy with urokinase and ascorbic acid is effective in preventing symptomatic vasospasm after aneurysmal SAH.

Adult↗
PubMed2000

Involvement of the actin cytoskeleton in the regulation of serotonin transporter (SET) activity: possible mechanism underlying SET regulation by protein kinase C.

Our previous report has revealed that PKC activation by 12-O-tetradecanoylphorbol 13-acetate (TPA) inhibited the uptake activity of serotonin transporter (SET), via an indirect mechanism unknown, but not likely via direct phosphorylation of SET by PKC (Sakai et al., 1997. J. Neurochem. 68, 2618-2624). To elucidate whether PKC can directly phosphorylate SET in vivo, FLAG-tagged SET (FLAG-SET) was expressed in COS-7 cells and the TPA-induced incorporation of (32)P into immunoprecipitated FLAG-SET was examined. PKC activation with TPA caused no phosphorylation of FLAG-SET expressed in COS-7 cells. On the other hand, morphological change associated with the disruption of filamentous actin (F-actin) was seen in TPA-treated COS-7 cells. Therefore, we studied the effects of cytochalasin D, an inhibitor of actin polymerization, on the uptake activity of the serotonin transporter (SET) to elucidate whether the actin cytoskeleton modulates the SET uptake activity. The treatment with cytochalasin D inhibited the uptake activity of both native and recombinant SET in a concentration-dependent manner. Eadie-Hofstee analysis revealed that cytochalasin D down-regulated the recombinant SET uptake activity by reducing the V(max), but not the K(m), mimicking the result observed in TPA-induced inhibition of SET activity (Sakai et al., 1997. J. Neurochem. 68, 2618-2624). The cytochalasin D-induced inhibition of SET activity was partially, but significantly, reversed by jasplakinolide, a cell permeable stabilizer of F-actin, whereas TPA-induced inhibition of SET activity was not reversed by jasplakinolide. To elucidate whether the subcellular localization of SET was changed in response to cytochalasin D or TPA, we expressed the SET fused with the green fluorescent protein (SET-GFP) in COS-7 cells and observed the subcellular distribution of SET-GFP under a confocal laser scanning fluorescent microscope. Neither cytochalasin D nor TPA markedly changed the SET-GFP cellular localization, although these drugs caused morphological change in the GFP-transfected COS-7 cells. In addition, SET activity was not altered by the treatment with either colchicine, an inhibitor of microtubule polymerization, or taxol, a stabilizer of microtubule polymerization. These results suggest that the SET uptake activity was regulated by the state of the actin cytoskeleton and that TPA exerts its inhibitory action on SET activity, in part, via disruption of F-actin and subsequent morphological change in cells.

Actins↗
PubMed2000

Urokinase cisternal irrigation therapy for prevention of symptomatic vasospasm after aneurysmal subarachnoid hemorrhage: a study of urokinase concentration and the fibrinolytic system.

BACKGROUND AND PURPOSE: Cisternal irrigation therapy with urokinase (UK) was performed in multiple institutions to prevent symptomatic vasospasm. The efficacy and safety of this therapy were evaluated, and the optimal concentration of UK was estimated. METHODS: This therapy was performed in 28 patients who underwent surgery within 72 hours of the onset of severe subarachnoid hemorrhage (Fisher's group 3, CT number [Hounsfield units] >60). After the aneurysm was clipped, irrigation tubes were placed in the Sylvian fissure (inlet) unilaterally and in the prepontine or chiasmatic cistern (outlet). Lactated Ringer's solution with UK (30, 60, or 120 IU/mL) was infused at a rate of 30 mL/h. The presence of symptomatic vasospasm was evaluated by changes in the clinical symptoms and the presence of a new low-density area on CT scan. Drained irrigation fluid and peripheral blood were examined chronologically to evaluate the fibrinolytic system. RESULTS: Symptomatic vasospasm was observed transiently in 3 cases (10.7%) without any low-density area on CT scan. In the 120-IU/mL group, no symptomatic vasospasm occurred. Analysis of drainage fluid suggested that UK 120 IU/mL is effective. The mean values of total drained blood volume for the respective groups were as follows: 58 mL in 30 IU/mL, 106 mL in 60 IU/mL, and 143 mL in 120 IU/mL. No abnormal changes were observed in the coagulative and fibrinolytic systems after UK irrigation. CONCLUSIONS: These results suggest that cisternal irrigation therapy with UK is safe and effective for the prevention of symptomatic vasospasm after aneurysmal subarachnoid hemorrhage.

Biomarkers↗